The present application relates generally to the field of retractors for use in occupant restraint systems (e.g., seatbelt systems). More specifically, the present application relates to retractors being configured with a load limiting device to provide energy management.
As shown in FIGS. 2 and 3, conventional retractors 1020 commonly utilize a torsion bar 1060 disposed within the spool 1062 of the retractor 1020 to provide energy management with the purpose of removing energy from the system during a dynamic vehicle event, such as a front-impact event. The torsion bar 1060 is generally made from steel to provide a constant load throughout their design range. As a result, the load management capability of the conventional retractor 1020 is limited to a single level of energy absorption, such as shown in FIG. 21, that compares a single level load limiter (e.g., a retractor having just a torsion bar) to a retractor disclosed below that includes a progressive load limiting device.
The National Highway Traffic Safety Administration (NHTSA) has recently amended its criteria for evaluating passenger vehicles under its New Car Assessment Program (NCAP). Previously, the NCAP evaluation was based on, among other things, the acceleration of the occupant (i.e., the number of G's or g-forces that the occupant was subjected to during the dynamic event). Accordingly, it was advantageous to provide a single level load limiter to thereby limit the acceleration of the occupant during dynamic vehicle events. Now, the NCAP evaluation is based on, among other things, the chest deflection (or displacement) and compression of the occupant during the dynamic vehicle event. Accordingly, it is now desirable to provide occupant restraint systems with energy management devices that limit the chest deflection (or displacement) and compression of the occupant during such events.